1. Field of the Invention
The present invention relates to a method and apparatus in which control systems are used to regulate various aspects of injection molding machine equipment (e.g., insert stacks or hot runner nozzle assemblies) in conjunction with active material element sensors and actuators. “Active materials” are a family of shape altering materials such as piezoactuators, piezoceramics, electrostrictors, magnetostrictors, shape memory alloys, and the like. Such control systems may be used in an injection mold to counter deflections in the mold structure, aid in ejection of molded articles, and apply vibration and/or compression to melt, thereby improving the quality of the molded articles and the life of the mold components. Injection molding equipment includes both molding a melt of plastic material and molding a melt of metal material, for example, a metal in a thixotropic state.
2. Related Art
Active materials are characterized as transducers that can convert one form of energy to another. For example, a piezoactuator (or motor) converts input electrical energy to mechanical energy causing a dimensional change in the element, whereas a piezosensor (or generator) converts mechanical energy—a change in the dimensional shape of the element—into electrical energy. One example of a piezoceramic transducer is shown in U.S. Pat. No. 5,237,238 to Berghaus. Marco Systemanalyse und Entwicklung GmbH is a supplier of peizoactuators located at Hans-Böckler-Str. 2, D-85221 Dachau, Germany, and their advertising literature and website illustrate such devices. Typically, an application of 1,000 volt potential to a piezoceramic insert will cause it to “grow” approximately 0.0015″/inch (0.15%) in thickness. Another supplier, Mide Technology Corporation of Medford, Me., has a variety of active materials including magnetostrictors and shape memory alloys, and their advertising literature and website illustrate such devices, including material specifications and other published details.
Intelligent processing is known in the art of injection molding. For example, U.S. Pat. No. 6,289,259 to Choi et al. discloses an intelligent hydraulic manifold device. A microcontroller is electrically coupled to a system controller to provide distributed control within the hydraulic circuit of an injection molding machine.